Fabricating transfer channel and charge trap in carbon nitride ultrathin nanosheet for enhanced photocatalytic hydrogen evolution

Fabricating environmental and stable graphitic carbon nitride (g-C 3 N 4 ) photocatalyst with highly efficient visible light response and charge separation is still a challenging work. Herein, g-C 3 N 4 ultrathin nanosheets are synthesized via oxidation etching method. The as-synthesized samples show improved visible-light response and photogenerated charge separation, which is revealed to be brought from the synergy of hierarchical porous structure and nitrogen vacancies. On one hand, macropores can provide light transport channels for enhanced visible light absorption , meanwhile the photogenerated charge favors to be migrated on two-dimensional ultrathin planes and trapped in mesoporous structure to avoid the recombination. Also, macropore and mesopore promote the transport and adsorption of substrates. On the other hand, DFT calculations verify that nitrogen vacancies are conductive to the rearrangement of charge density distribution and the formation of defect levels in the band gap of g-C 3 N 4 , leading to the improvement of carrier mobility and separation. Thus, nitrogen vacancies promote more active sites generation. Consequently, the g-C 3 N 4 ultrathin nanosheet presents a promising photocatalytic hydrogen evolution rate of 1.77 mmol .g −1 .h −1 in a long time run under visible light, which is far higher than that of comparison samples (0.18 and 0.29 mmol .g −1 .h −1 respectively).